Generally described, a gas turbine bucket often includes an elongated airfoil with an integrated tip shroud attached thereto. The tip shroud attaches to the outer edge of the airfoil and provides a surface that runs substantially perpendicular to the airfoil surface. The surface area of the tip shroud helps to hold the turbine exhaust gases onto the airfoil such that a greater percentage of the energy from the turbine exhaust gases may be converted into mechanical energy. This increased percentage generally leads to an increase in overall turbine efficiency and performance. The tip shroud also may provide aeromechanical damping and shingling (fretting) prevention to the airfoil. Many different types of turbine bucket, airfoil, and tip shroud configurations may be used.
The connection between the tip shroud and the airfoil may become highly stressed during operation because of the mechanical forces applied via the rotational speed of the turbine. When these mechanical stresses are coupled with the thermal stresses and high metal temperatures associated with the harsh operational environment of the turbine, overall performance may be compromised over the useful lifetime of the airfoil. Reducing the metal temperatures experienced by the tip shroud by cooling it during operation could extend the useful lifetime of the component. The use of such cooling flows, however, may reduce overall efficiency. Moreover, the cooling flows may be reduced or ineffective because of the segment gaps between adjacent bucket tip shrouds.
There is thus a desire for an improved turbine bucket tip shroud. Such an improved turbine bucket tip shroud may provide optimized cooling so as to reduce the sensitivity to bucket segment gaps while increasing the overall lifetime of the component for improved reliability and availability.